The present application relates to measuring radiation attenuation by an object exposed to radiation. It finds particular application in the field of computed tomography (CT) imaging utilized in medical, security, and/or industrial applications, for example. However, it also relates to other radiation imaging modalities where converting radiation energy into digital signals may be useful, such as for imaging and/or object detection.
Radiation imaging modalities such as CT systems, single-photon emission computed tomography (SPECT) systems, digital projection systems, and/or line-scan systems, for example, are useful to provide information, or images, of interior aspects of an object under examination. Generally, the object is exposed to radiation comprising photons (e.g., such as x-rays, gamma rays, etc.), and an image(s) is formed based upon the radiation absorbed and/or attenuated by the interior aspects of the object, or rather a number of radiation photons that are able to pass through the object. Generally, highly dense aspects of the object absorb and/or attenuate more radiation than less dense aspects, and thus an aspect having a higher density, such as a bone or metal, for example, will be apparent when surrounded by less dense aspects, such as muscle or clothing.
The detector array typically comprises a plurality of detector cells, respectively configured to convert detected radiation into electrical signals. Based upon the number of radiation photons detected by respective detector cells and/or the electrical charge generated by respective detector cells between samplings, images can be reconstructed that are indicative of the density, z-effective, shape, and/or other properties of the object and/or aspects thereof.
The number of detector cells comprised within a detector array may be application specific. For example, in security applications where it is desirable to continuously translate an object (e.g., on a conveyor belt) while acquiring volumetric data about the object, the number of detector cells may exceed 100,000. In other applications, such as in mammography applications where the object is stationary and two-dimensional data is acquired, the number of detector cells may exceed 10,000,000.
To, among other things, facilitate a modular design of detector arrays, self-contained detector units (e.g., also referred to as tiles) have recently been developed. Respective detector units comprise a plurality of detector cells (e.g., 128 detector cells, 256 detector cells, etc.) and can be arranged with other detector units to form a detector array having a desired number of detector cells, a desired size, and/or a desired shape. For example, U.S. Pat. No. 7,582,879, assigned to Analogic Corporation, describes a self-contained detector unit that comprises, among other things, a scintillator, a photodetector array, and an integrated circuit (e.g., comprising, among other things, an A/D converter).